The stable isotopes of O, H, C and N are not only essential for life, but also make up over 97% of the hydrosphere and atmosphere, and over 50% of the earth´s crust. This makes them excellent natural tracers of geochemical and biogeochemical processes, which allow precise quantification of the interactions between the geosphere, hydrosphere, atmosphere and biosphere. Chemical and physical processes that occur in natural systems result in changes in the ratios of stable isotopes (13C/12C, 18O/16O, 15N/14N, 34S/32S and D/H). The study of this so called isotopic fractionation represents a powerful tool for determining the origin of both organic and inorganic compounds. It enables the construction of natural records and of paleoclimatic, paleoenvironmental, paleohydrological and paleodietary information, as well as enabling the creation of predictive models for future scenarios of climatic evolution.